Process for the production of formaldehyde-cyclic formal copolymers



United States Patent 3,346,540 PROCESS FOR THE PRODUCTION OF FORMALDE- HYDE-CYCLIC FORMAL COPOLYNIERS Tamotsu Eguchi and Junnosuke Yamauchi, Kurashiki,

Japan, assignors to Kurashiki Rayon Company Limited,

Kurashiki, Japan, a corporation of Japan No Drawing. Filed June 15, 1964, Ser. No. 375,385 Claims priority, application Japan, June 20, 1963, 38/259 4 Claims. (Cl. 260-67) This invention relates to a process for the production of a novel formaldehyde copolymer particularly by copolymerizing cyclic formal and formaldehyde in the presence of an acidic catalyst,

The object of the invention is to provide a high molecular weight formaldehyde copolyrner which provides fibers, plastics and films, having superior thermal stability, high chemical resistance, excellent mechanical properties (especially, high tensile strength, excellent toughness and high modulus).

Polyoxymethylene that has been widely used as plastics and fibers is a homopolymer of formaldehyde. This is produced by polymerization of formaldehyde, followed by etherification or esterification of the hydroxyl group as the terminal group with an etherification or esterifica- 7 tion agent. If only formaldehyde is polymerized, the stabilization of the terminal group is indispensable. The stabilization itself takes a great deal of time and money due to the additional chemicals, polymer washing and stabilizing apparatus, and furthermore causes a loss often several percent of the polymer charge for the treatment due to the depolymerization thereof. Since the main chain of the stabilized polymerrnolecule consists of recurring CH -O units (this polymer is designated as polyoxymethylene), the following defects res'ulting'from such structure cannot be avoidable. That is, this. polymer is apparently stable, but due to the .irradiationof ultraviolet ray, oxidation in air, high temperature heating and immersion in alkalis, the deesterification or deetherification of the terminal group and the oxidative fission of the chain occur and subsequently a rapid depolymerization reaction occurs from that part, resulting in releasing formaldehyde monomers. Consequently, moldings of this polymer cannot be used widely.

In order to overcome such defects in the production of the formaldehyde polymer and in the product itself, the inventors have improved the polymer by copolymerizing formaldehyde and cyclic formal thereby to introduce a different linkage (four carbon atoms bonded group) formed by the, ring-opening of the cyclic formal into the polyoxymethylene group. As a consequence it can be found that such improved polyoxymethylene can be produced at lower cost because of that the stabilization of the terminal groupis not necessary and can be found a wide use because of its high heat resisting property, as compared with the known polyoxymethylene.

The term acidic catalyst in this specification means metal halides of Lewis acid type uch as boron trifluoride, boron trifluoride ethyl-etherate, ferric trichloride, tin tetrachloride, titanium tetrachloride, aluminum trichloride, a complex compound formed between such metal halide and a weak basic compound such as amine or ether, a mineral acid such as sulfuric acid and hydrochloric acid,

and acidic material such as 'p-toluene sulfonic acid.

The term cyclic formal in this specification means a cyclic formal selected from a structure of seven membered ring or more (I) and a structure of eight membered ring or more (II).

O (0 Hz) m-O (C R1Rz) CHa X CH, O (O Hz) m-O 10 (II) formal, y, 'y'-dioxy-dipropylsulfo formal and N-methyl bis (fi-oxyethyl) amine formal.

These cyclic formals can be produced by dehydrating reaction of linear glycol and formaldehyde. In the invention, the proportion of the cyclic ether contained in the copolymer is 0.1 2 0 to 100 CH O units, and in particular the preferred portion is 0.5-3.0.

The polymerization reaction of the invention is car- 3 ried out by contacting an acidic catalyst, cyclic formal and formaldehyde simultaneously. The catalyst and two monomers may be in gaseous or liquid state. The use of a suitable inert liquid medium may assist the smooth simultaneous contact of the acidic catalyst and two monomers and, in addition, may facilitate to take out the produced polymer. Such inert liquid mediums are benzene,

Xylene, toluene, ethers, chloroform, methylene chloride and a hydrocarbon solvent having a slight solubility for formaldehyde such as hexane and heptane. This solvent does not react with the acidic catalyst and monomers during the polymerization and may be a non-solvent for the produced copolymer.

A polymerization system or process for carrying out the invention may be any one of contacting the catalyst and two monomers simultaneously. Therefore, as the with the polymerization system or process, as illustrated I hereinafter. That is a system which comprises supplying continuously a catalyst and cyclic formal in a gaseous suspended state (for example, spraying in aerosol by use ofa small amount of a solvent 'such as hydrocarbon) to a polymerization reactor, at the same time introducing gaseous formaldehyde thereinto continuously thereby to carry out copolymerization in gaseous phase, and discharging the copolymer powder fallen from the lower part of the polymerization reactor, a system which comprises supplying a toluene solution of formaldehyde and cyclic ether continuously to a polymerization reactor, at

the same time introducing .a toluene solution of a catalyst thereinto continuously thereby to carry out solution polymerization system, a batch system, continuous syspolymerization and discharging the resultant slurry of the copolymer, or a system which comprises supplying a toluene solution of a catalyst and cyclic formal to a polymerization reactor equipped with a stirrer, in which but a random copolymer. This will be based upon the similarity of the molecular reactivity ratio of the cyclic formal of the invention with that of formaldehyde.

When the structure I, for example, 1,4-butanediol a solvent such as toluene is charged, at the same time in- 5 formal is selected as a comonomer, a group of troducing gaseous formaldehyde continuously into the reactor to carry out copolymerization in the toluene sol C C C C OC vent and discharging the resultant slurry of the copolyis consequently introduced as a different linkage. If b utylmer from the reactor. ene oxide is selected as the comonomer, the same dif- The polymerization reaction of the invention may be ferent linkage must be consequently introduced. However, carried out at a suitable temperature. The temperature it is difficult to produce the random copolymer from such used practically is from l00 C. to +100 C. In par higher alkylene oxide as butylene oxide, as far as an ticular, when the solution Polymerization i g a s l acidic catalyst is used under the condition of the present is carried out, it is preferred to select a temperature sufinvention. Its molecular reactivity ratio is lower as comficient to keep the system at a stable liquid state in 216- pared with that of formaldehyde and, in general, only the cordance with the solubility of formaldehyde. The cohomop-olyrner of formaldehyde is produced. polymerization reaction of the invention is ordinarily carried out at atmospheric pressure and may be carried 3-Molecular welght of the copolymer out at above of below atIIIOSPheTic Pressure The two It is evident from Table 1 that the molecular Weight of monomers used must be Purified Previously in Parthe copolymer of the invention is higher than that of ticular, chain transfer agents such as water and methanol h known copolymer f formaldehydg i h a comonomer must be removed as far as Possible such as alkylene oxide and the copolymer has the excelv PL for the eopolymeriza-tion y the inVeIllent mechanical properties than the known copolymer. It tiofl is much Superior to those of the Prior art, as H1115 is considered that this is based upon the copolymerizing trated hereiflafterproperty of cyclic formal and, in addition, the easiness of Stability and alkali resistance the purification of cyclic formal. The cyclic formal of property of the copolymer the structures I and Il may be chargedto a polymer zatron reactor immediately after the slmple distillation The first order thermal decomposition velocity con- Without a special purification star of the Polymer at 1s des lgnated as Km, The following examples will illustrate the invention which unit is represented by percent/minute. When the further in detaiL ring of the cyclic formal represented by the structure I EXAMPLE 1 described hereinbefore is opened and copolymerized, four or more carbon atoms linked groups are introduced, ml. of purified toluene and 15 ml. of 1,4-butanediol resulting in improving the thermal stability as evident 35 formal were placed in a 200 ml. 4-necked flask equipped from the Table 1. Similarly when the cyclic formal repwith a stirrer, cooler at the top of which a silica gel tube resented by the structure II is used, two carbon atoms for drying is provided to prevent from the moisture, linked groups are introduced into the chain. thermometer and dropping funnel and the mixture was TABLE 1 Conversion of copolymer after purified Polymerization Polymerization homopolymer- N0- Comonomer process solvent and lzation of temp. C) comonomer K (per- (1,) (dl./g.)

(percent)* cent/min.)

1. Method of the 1,4-butanedlol formal (structure I) Solution process--. Toluene, 20" C.- 2 0.002 2.0 2. invention. {Diethyleneglycol formal (structure II) ..d0 Toluene, --78 C. 3 0.007 1.6 3 None (homo-polymer of formalde- Bubbling process. n-Hexane, 30 C 1.60 1. 6 4 Known method- {Etiiigigiie oxide Solution process.-. Toluene 20 C-- 10 0.010 1.0 5..." Isobutylene do Haxane, 78 C"... 15 0.025 0.4

This means the value based on monomer charged.

2.Copolymerization reactivity When the cyclic formal of the invention is used, the copolymerization reaction with formaldehyde can proceed substantially. The yield of the copolymer is high and the conversion of homopolymerization of the cyclic formal is as little as can be neglected. That is, it is made clear by the analysis of the copolymer that the cyclic formal of the invention is effectually consumed only for the production of the copolymer under a wide condition and furthermore the produced copolymer is not a block copolymer,

cooled to 78 C. 13.7 g. of purified liquid formaldehyde was added thereto and stirred to give a uniform transparent liquid. Then, a catalyst solution obtained by dissolving 0.1 ml. of boron trifluoride-diethyl ether complex in 50 ml. of toluene was dropwise added with stirring. The polymerization commenced at the same time as the dr opwise addition of the catalyst solution and a white slurry was formed because of the deposition of the polymer. The temperature rose due to the heat of polymerization and reached 35 C. after 15 minutes since the end of the addition of the catalyst. After stirring at -3S C. for 3 hours, the product was filtered, washed with a hot aqueous solution of 5% sodium carbonate to neutralize the catalyst, with hot water, and with acetone, and dried overnight at 60 C. in vacuo to give 14.2 g. of a white powdered polymer. 10 parts of the resulting crude copolymer were introduced into parts of benZyl alcohol containing 0.5% of tributylamine and held at C. for 30 minutes for the purification thereof. After cooling by standing, the deposited polymer was filtered, washed with methanol and acetone, and dried overnight at 60 C. in vacuo to give 6.5 parts of a purified white powdered polymer. The purifying yield was 65%.

0.5% of polyurethane and 0.5% of diphenylamine were added to the purified polymer. The value of K of the mixed powder was 0.003 min.

and 1,3-dioxolane were purified in the same manner as in Example 1. The results of the comparison examination about the thus purified copolymers are given in the following Table 2.

TABLE 2 [Properties of copolymer of formaldehyde and 1,4-butanediol formal and that of formaldehyde and 1,3-dioxo1ane] Content of Yield of the formal [1,] (dl./g.) K i Sample purification unit in of purified Strength (percent/ (percent) purified copolymer min.) polymer (mol percent) Copolyrner of 1,4butanediol formal.-. 81. 2 1. 3 1. 22 Excellent 0. 003 Copolymer of 1,3-dioxolane 69. 1 0. 7 0. 66 None 0. 02

First order constant of thermal decomposition velocity of purified polymer added with 0.5% of polyurethane and 0.5% of diphenylamine.

The melting point of the copolymer was 168 C. and the copolymer contained 1.2 mol percent of butanediol formal unit by the elementary analysis. When the purified copolymer powder was pressed at 190 C. and 200 kg./ cm. a tough, stiff, translucent film was given.

EXAMPLE 2 90 ml. of purified toluene and 12.5 ml. of butanediol formal were introduced into an autoclave and a small ampule including a solution of 0.1 ml. of boron trifluoride ethyl etherate in 10 ml. of toluene was introduced thereinto. The autoclave was cooled to 78 C. then g. of liquid formaldehyde cooled to 78 C. was added after evacuating the inside thereof. After being closed, the autoclave was taken out of a bath of dry ice-methanol at 78 C. and left standing. When the temperature of the inside rose to room temperature, the small ampule including the catalyst was broken by oscillation. The copolymerization reaction commenced and the temperature rose to 50 C. After the oscillation of the autoclave for 1 hour, the product was discharged, filtered, washed with a hot aqueous solution of 5% sodium carbinate,

hot water, and acetone, and dried at 60 C. in vacuo to give 21.1 g. of a-crudecopolymer. 21.1 g. of the crude copolymer was purified in the same manner-as in Example 1 to give 18.2 g. of a purified copolymer. The a content of butanediol formal in the purified copolymer was 1.8 mol percent by the result of the elementary analysis thereof. The intrinsic viscosity thereof in p-chlorophenol containing 2% wpinene at 60 C. was 1.5 dL/g. The K value of the mixture of the 99.0% copolymer, 0.5% of polyurethane and 0.5% of diphenylamine was 0.006%/min. and its thermal stability was much more excellent.

EXAMPLE 3 100 ml. of purified toluene, 2.5 ml. of l,4-butanediol formal (0.0245 mol) and 0.1 ml. of BF OEt were placed in a 4-necked flask equipped with a stirrer, reflux condenser at the top of which a silica gel tube was equipped, thermometer and an inlet and the flask was imrnersed in water bath at 40 C. Formaldehyde gas was introduced into the flask at a rate of '20 lit/hour through an inlet, then immediately the polymerization occurred and the polymer was deposited and slurried. After the introduction of formaldehyde gas for 1 hour, the slurry was filtered, Washed with a hot aqueous solution of 5% sodium carbonate to neutralize the catalyst, with hot water and with acetone, and dried at 60 C. in vacuo to give 18.3 g. of the polymer. On the other hand, 1,3-dioxolane was copolymerized with formaldehyde to give 16.0 g. of a polymer in a manner similar to that described as above except that 1.9 ml. of 1,3-dioxolane (0.0245 mol) was used in place of 2.5 ml. of 1,4-butanediol formal (0.0245 mol). 7

The resulting copolymer of crude formaldehyde and 1,4-butanediol formal and that of crude formaldehyde The copolymeriz ation was carried out under the same condition as in Example 3 except that the quantity of charging materials was changed as follows:

7 M1. Toluene 1,4-butanediol formal 1.0 BF3'OEt2 Thus 21.7 g. of crude copolymer was obtained. This crude copolymer was purified in the same manner as in Example 1 and 16.4 g. of a purified copolymer was ob tained. a

I EXAMPLE 5 The copolymerization was carried out under the same condition as in Example 3 except that the quantity of charging materials was changed as follows:

Ml. Toluene 100 1,4-butanediol' formal 10 BF3'OEt2 0.1

Thus 20.9 g. of crude copolymer was produced. This crude copolymer was purified in' the same manner as in Example 1 and 18.6 g. of a purified copolymer was obtained.

In the following Table 3, the melting points, compositions, intrinsic viscosities 1] and K values of the copolymers obtained in the examples described as above are shown:

TABLE 3 1,4-butauediol Melting formal in [1,] Km (percent! Examples point C.) purified Copolymer min.)

copolymer of (dl./g.) (mol percent) EXAMPLE 6 A vertical cylindrical reactor (10 cm. inner diameter and 50 cm. height) was employed. At the upper part of the reactor three inlets for gaseous formaldehyde, a catalyst and formal were provided and at the lower part thereof an outlet for'a powdered copolymer and an exhaust port were provided. Gaseous formaldehyde at a rate of 20 g./hour and a solution containing 25 g. of 1,4-butanediol formal per 1000 ml. of petroleum ether at a rate of 200 mL/hour were introduced into the reactor from the upper part thereof so as to form a gaseous suspension and at the same time gaseous boron trifluoride was introduced at a rate of 0.2 g./hour. Then the copolymerization reaction commenced immediately and copolymer granules fell to the bottom, the discharge of which was conducted periodically. The petroleum ether used was completely vaporized due to the heat of polymerization and discharged from the exhaust port at the lower part. The yield of the copolymer was substantially quantative. g. of the copolymer powder taken out of the outlet were purified in the same manner as in Example 1 to give 4.1 g. of a purified copolymer. The result of the elementary analysis of the purified polymer showed that it contained 1.5 mol. percent of butanediol formal. The intrinsic viscosity thereof in p-chlorophenol containing 2% of a-pinene at 60 C. was 1.4 dl./g.

EXAMPLE 7 1,5-pentanediol formal was copolymerized with formaldehyde to produce 21.5 g. of a crude copolymer in the same manner as in Example 3 except that 2.5 ml. of 1,5- pentanediol formal were used in place of 1,4-butanediol formal of Example 3. The crude copolymer was purified in the same manner as in Example 1 to give 17.8 g. of a purified copolymer. The intrinsic viscosity of the copolymer in p-chlorophenol containing 2% of a-pinene at 60 C. was 1.2 dl./g. The K of a mixture of 99.0% of the purified copolymer, 0.5% polyurethane and 0.5 diphenylamine was 0.008% /min. and the thermal stability was very excellent.

EXAMPLE 8 Formaldehyde was copolymerized with diethyl glycol formal in the same manner as in Example 1 except that 2.5 ml. of diethylene glycol formal were used in place of 2.5 ml. of 1,4-butanediol formal of Example 3 and 20.7 g. of a crude copolymer were obtained. The crude copolymer was purified in the same manner as in Example 1 to give 15.5 g. of a purified copolymer. The melting point of the purified copolymer was 170 C. and the result of the elementary analysis showed that it contained 1.2 mol percent of diethylene glycol unit. The intrinsic viscosity thereof in p-chlorophenol containing 2% of a-pinene at 60 C. was 1.3 dL/g. The K of a mixture of 99.0% of the purified copolymer, 0.5% of polyurethane and 0.5 of diphenylamiue was 0.007%/ min. and the heat stability was good.

EXAMPLE 9 The copolymerization was carried out under the same condition as in Example 3 except that chloroform was used as copolymerization solvent in place of toluene as follows:

Chloroform 100 1,4-butanediol formal 2.5 BF -OEt 0.1

Thus 21.2 g. of crude copolymer were produced. This crude copolymer was purified in the same manner as in Example 1 and 19.9 g. of a purified copolymer were obtained. The result of the elementary analysis of the purified polymer showed that it contained 2.1 mol percent of butanediol formal. This intrinsic viscosity in p-chlorophenol containing 2% of a-pinene at C. was 1.5 dl./ g.

What we claim is:

1. A process for the production of high molecular weight formadehyde copolymers having improved thermal stability which comprises contacting the ingredients of a mixture consisting essentially of an acidic catalyst, formaldehyde and a cyclic formal represented by the structure (oHnmo X/ CH 2)m wherein X is selected from the group consisting of O, S, NH and NR in which R is lower alkyl group and m is an integer selected from 2 and 3, said cyclic formal being used in the amount from 0.1 to 20 moles per moles of formaldehyde.

2. A process according to claim 1, wherein the reaction is carried out at a temperature from minus 100 C. to plus 100 C.

3. A process according to claim 2, wherein the reaction is carried out in an inert liquid.

4. A process according to claim 1, wherein said acidic catalyst is selected from the group consisting of boron trifluoride, boron trifiuoride ethyl-etherate, titanium tetrachloride, tin tetrachloride and aluminum trichloride.

References Cited UNITED STATES PATENTS 3,194,788 7/1965 Kullmar et al 26067 3,197,420 7/1965 Weissermel et al 2602 3,256,246 6/ 1966 Gutweiler et al 26067 FOREIGN PATENTS 1,271,297 7/1961 France. 1,346,542 11/ 1963 France.

OTHER REFERENCES Kern et al. Journal of Polymer Science, vol. 48, No. 150, pp. 399-404, December 1960.

WILLIAM H. SHORT, Primary Examiner.

L. M. PHYNES, Assistant Examiner. 

1. A PROCESS FOR THE PRODUCTION OF HIGH MOLECULAR WEIGHT FORMADEHYDE COPOLYMERS HAVING IMPROVED THERMAL STABILITY WHICH COMPRISES CONTACTING THE INGREDIENTS OF A MIXTURE CONSISTING ESSENTIALLY OF AN ACIDIC CATALYST, FORMALDEHYDE AND A CYCLIC FORMAL REPRESENTED BY THE STRUCTURE 